Email in my sent items that I did not send

I just noticed I have an email in my sent items that I did not send.

It was reporting a receipt for a donation that I just made using paypal. From an internet search, some people think this may have something to do with zone alarm, however, no place in the email is zone alarm mentioned.

Three things concern me

(1) I did not send the email

(2) The email has an encrypted portion so I don't know what is being included.

(3) I don't have any idea what program or service caused the email to be sent.

If this was a legitimate za email, I assume that the email would give information that it was being sent by za and za should have asked me.